1. Field of the Invention
This invention relates to a boomerang for sport, more particularly to a boomerang made from a flat sheet material and having blades formed with bent portions for creating a lift during flight.
2. Description of the Related Art
Conventional boomerangs for sport are generally required to have a sufficient thickness in order to produce a desired lift according to Bernoulli""s law, thereby resulting in a greater weight thereof, which in turn results in a larger flight range. Therefore, the conventional boomerangs as such generally cannot be used in a relatively narrow area.
Another type of boomerang is proposed to be made from a thin plate so as to reduce the overall weight of the boomerang. However, as the flight radius of the boomerang is relatively small and as the flight path thereof is monotonous, the boomerang is not interesting to play with.
The object of the present invention is to provide a boomerang which can be manufactured easily and which permits control of flight patterns thereof.
According to this invention, the boomerang is made from a flat sheet material, and includes a central body with an outer periphery surrounding a center point. The central body has top and bottom surfaces substantially parallel to each other and in symmetry to a horizontal plane. A plurality of interconnecting portions are integrally formed with the outer periphery of the central body, and are angularly displaced from one another about the center point. Each of the interconnecting portions extends outwardly and along a radial axis, and terminates at an arc boundary. The arc boundaries of the interconnecting portions cooperatively define a circumference having a radius. A plurality of blades are formed integrally and respectively with the interconnecting portions, and are angularly displaced from one another. Each of the blades includes leading and trailing edges which are opposite to each other in one of clockwise and counterclockwise directions when the blades are turned about an axis that is normal to the horizontal plane, and that passes through the center point. Each of the blades further includes a distal edge which is opposite to the arc boundary of the respective one of the interconnecting portions, and which joins with the leading and trailing edges at leading and trailing junctures, respectively. Each of the blades further includes a bent line which extends from an outer point at the distal edge to an inner point at the are boundary, and which is of a length that is equal to the radius. The bent line meets a radius line at the arc boundary to form a vertex with an included angle of obtuseness that faces towards the leading edge. A bent portion is formed by the bent line and the trailing edge, and forms with the horizontal plane an included angle of obtuseness that faces downwards.